Is Simovis or PC-IN the only options for accessing an early CU1 version? I would prefer Drive Monitor it apparently lacks a definition for the early version, mine only has v1.3 for the FC/CU1.

DriveMonitor V5.1 SP1HF1 supports the following devices and actual firmware versions:
It goes without saying that all of the previous firmware versions of the units are supported.

...MASTERDRIVES CU1( V1.3 )...

Even in last version of DriveMon you can see same text. In the other way, you are right. Only v1.3 is possible to be selected in DriveMonitor. I suggest you to contact with Siemens Hotline and ask how to proceed in his case.

regards